DELPHI

Overview

DELPHI was one of four large detectors on the Large Electron-Positron collider (LEP). It took 7 years to design and build, and it started up in 1989. In December 2000, DELPHI stopped taking data and was dismantled to leave room for the construction of the Large Hadron Collider in the LEP tunnel.

DELPHI consisted of a central cylinder filled with subdetectors, with two end-caps. It was 10 meters in length and diameter, and weighed 3500 tons. The detector consisted of 20 subdetectors. A large superconducting magnet sat between an electromagnetic calorimeter (for tracking electrons) and a hadronic calorimeter (to detect hadrons). The magnet generated a field to deflect charged particles so their charge and momenta could be measured.

The collaboration running the detector consisted of about 550 physicists from 56 participating universities and institutes in 22 countries.

Computing Environment

The OPAL computing environment is availabale using CernVM. The virtual machine environment can be created by running CernVM with the cloud-init user data file for delphi: delphi.yaml. It will be easiest to run the CernVM on the CERN OpenStack, for more information consider these websites: cern.ch/cernvm and cern.ch/clouddocs. Some instructions for the use of the cloud-init user data is imbedded in the file, look though the file.

The virtual machine configured by the cloud-init user data lets you connect to eos to access the experiment data. The software environment for the experimnet is provided using cvmfs. You need to run the VM in a context where it can access these services.

Bit Preservation:

State of the art bit preservation with regular scrubbing and migration to new media.

Data:

Two copies on tape at CERN, one copy on disk, and one copy at external institute (University of Cantabria, Santander) with tape archive.

Documentation:

To be archived in CERN Document Server for long-term preservation. Some software documentation on CernVMFS alongside the code.

Software:

Binaries and source code published into CernVMFS. Software CD on AFS at CERN.

Use Cases:

Continued analyses by former collaboration members. Discussing open access publication for education and outreach.

Audience:

Primarily former collaboration. Open access data targeted at physicists and students, to be approved by the collaboration.

Value:

Analyses, publications and PhDs continue to be produced

Uniqueness:

Unique – until and unless certain FCC options are implemented

Resources:

Minimal resources for bit preservation and storage. WLCG infrastructure for software on CVMFS.

Status:

Data and simulated events are available on EOS. A DELPHI collaborator using CernVM may reconstruct and analyse the data and generate Monte Carlo events.

Issues:

Dependency on CERNLIB and 32-bit architecture (no longer maintained)

Outlook:

Expect to be able to analyse data until at least 2020. Until 2030 should be possible with < (<) 1FTE / year